1. Field of the Invention
The invention relates to warning devices that give notice of the use of speed detectors, for example by law enforcement agencies, such as radar detectors. More particularly, the invention relates to such systems that employ multiple receivers to increase reliability and lead time of warnings.
2. Background
Many operators of motor vehicles utilize radar detectors to alert them to the fact that their speed is being monitored by law enforcement agencies. However, conventional radar detectors often generate xe2x80x9cfalse alarms.xe2x80x9d They are also prone to respond too late, giving the vehicle operator insufficient time to adjust speed.
False alarms are annoying to the operators of motor vehicles. In fact, various automotive publications publish results of xe2x80x9cfalse alarmxe2x80x9d tests. Thus, anything that can be accomplished by the manufacturer to reduce the number of false alarms without reducing detection of police radar is commercially valuable
In addition to police radar signals, there are many different sources of microwave signals in the frequency bands allocated to police radar by the U.S. Federal Communications Commission (FCC). For example, motion-detecting burglar alarms and automatic door openers also operate in the frequency bands allocated to police radar. Thus, a need exists for a radar detector that can distinguish between signals generated by a police radar transmitter and those generated by other devices that utilize microwave signals within the same frequency bands.
As is known in the art, speed detection systems may be used to determine the speed of moving objects, such as ground based or airborne motor vehicles for example. It is often desirable for the operator of the moving vehicle to know when the speed of the vehicle is being measured. For example, it may be desirable for an operator of a moving automobile to know when the speed of the automobile is being detected by a speed detection system.
As is also known, such speed detection systems may utilize either radar or laser devices in their operation. A speed detection system that utilizes radar may generally be referred to as a so-called radar gun. Radar guns typically include a microwave signal source that emits a signal having a frequency in either the X, K or Ka frequency regions of the electromagnetic spectrum. Furthermore, radar guns may emit signals in either a continuous or a pulsed mode.
A laser speed detection system or so-called laser gun, on the other hand, includes a laser, which is a device that converts input power into a very narrow, intense beam of coherent energy at a single optical frequency, generally, but not necessarily, within the visible to infrared frequency region of the electromagnetic spectrum. Like radar guns, laser guns may also operate either continuously or in a pulsed mode. Laser guns generally operate in a pulsed mode due to input power requirements, cooling problems, and other considerations of the laser. The pulse width of the output of a pulsed laser is typically on the order of nanoseconds or picoseconds.
As is also known, there exists two particular classes of detecting systems generally referred to as radar detectors and laser detectors. A radar detector is a device used to detect the presence of a radar gun. A laser detector, on the other hand, is a device used to detect the presence of a laser gun. Typically, devices which detect the presence of radar guns are unable to detect the presence of laser guns. Similarly, devices capable of detecting the presence of laser guns are unable to detect the presence of radar guns.
Radar detectors typically detect signals having frequencies in the X-band, K-band and Ka-band frequency ranges. Such radar detectors often include a fixed frequency oscillator which generates a signal in the X-band frequency range. The so-called third harmonic of some X-band signals, however, fall generally within the Ka-band frequency range. Thus, one problem with conventional radar detectors which detect signals in the Ka-band frequency range is that such radar detectors may provide an alarm in response to the third harmonic signal of the fixed frequency oscillator of a nearby radar detector rather than in response to a signal emitted from a radar gun. This is generally referred to as a xe2x80x9cfalse alarmxe2x80x9d or simply xe2x80x9cfalsing.xe2x80x9d
Laser detectors also have problems with sounding false alarm signals in response to light signals emitted from sources other than laser guns. Laser detectors may also pose an additional problem in that they may be expensive, and may require accurate or pre-determined alignment or positioning of the laser detector within the path of a laser beam in order to function properly. Such systems are thus impractical for use by personnel on moving airborne and ground-based vehicles.
It would, therefore, be desirable to provide a detection device which detects the presence of both laser and radar speed detection systems and which is able to distinguish between signals provided from speed detection systems and signals provided from other detection devices such as other radar detectors. The other problem with all types of detectors is the extremely short notification provided by them. A driver has little time to adjust his/her speed after the warning is given before a speed estimate is generated by the scanning device used by the law enforcer. Thus, there exists a need in the art to provide more advanced warning of the use of laser, radar, and other scanning devices.
The invention provides a mechanism whereby detectors of speed detection devices, such as laser and radar speed detectors, communicate with each other so that each detector can use information available from other detectors to provide early warning and reliable detection. Each detector may be equipped with a radio transmitter and receiver. Upon detection of probe signal, a data signal is generated and received by all detectors in the vicinity. Recipients of the signal may generate a warning or use the information to generate a reliability metric to determine whether a warning should be generated.
The invention will be described in connection with certain preferred embodiments, with reference to the following illustrative figures so that it may be more fully understood. With reference to the figures, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.